Food handling implements such as tongs find wide-spread use in restaurants, diners, cafeterias and households for serving, grasping and generally handling a variety of food items. A variety of designs of tongs for handling food are known in the art, but generally comprise a pair of similar arms arranged in a mutually-opposing and spaced-apart relationship at one end for grasping food, and joined or connected at the other non-grasping or fulcrum end. The mutually-opposing and spaced-apart ends of the pair of similar tong arms are relatively moveable for grasping food items therebetween by a user single-handedly.
In some other complex designs, which are typically made of metal, the tongs may further include a separate hinge or pivot mechanism at the connected or fulcrum end and an additional spring mechanism for keeping the arms normally biased in a spaced apart relationship and lightly resistant to a closing force such as supplied by the gripping pressure of a user's hand. Other food handling tongs are fashioned in the form of scissors wherein the pivotal connection between the opposing arms is located between the grasping end and the handle end.
Usually in plastic tongs the arms are arranged in a spaced-apart fashion in the as-molded condition at one end, which can then be brought together for grasping food objects by a user's one handed grip. The arms are connected at the other end or fulcrum end. Disposable plastic tongs generally do not include any separate hinge and spring mechanisms and are generally molded from a material having sufficient inherent flexibility and resilience. Although, a multitude of resins can be utilized for making tongs; typical material choices for making disposable tongs include general purpose polystyrene (GPPS), polypropylene (PP), polyethylene terephthalate (PET), and blends of general purpose polystyrene (GPPS) and high-impact polystyrene (HIPS) resins. Typical prior art designs that have also been sold by the assignee of the present invention are shown in FIGS. 1A through 2D.
Tongs according to prior art Design “A” are shown in FIGS. 1A and 1B, wherein like parts bear like reference numerals. Specifically, tongs 10 have two similar arms 12 and 14 which are joined or connected at the fulcrum end 15. The term fulcrum end is used to describe the connected end of the tongs which allows arms 12 and 14 of tongs 10 to function as cooperative levers for grasping food items. The gate area for mold filling is centrally located at the fulcrum end 15 and is indicated by reference numeral 16. The grasping end of arm 12 is indicated by reference numeral 11 and the grasping end of arm 14 is indicated by reference numeral 13. The grasping ends 11 and 13 are mutually-opposed and in the as-molded condition are spaced-apart as shown in FIGS. 1A and 1B. During actual use, arms 12 and 14 are squeezed together whereby grasping ends 11 and 13 are brought in a closed position relative to each other for grasping food items by a user single-handedly. One of the problems with this design is that the tongs tend to fail in the fulcrum region or around the gate area. It would be appreciated by those skilled in the art that when arms 12 and 14 are brought closer together the inner areas in the fulcrum region undergo compressive stresses while the outer areas are subjected to tensile stresses.
Tongs according to prior art Design “B” are shown in FIGS. 2A through 2B, wherein like parts bear like reference numerals. Specifically, tongs 20 have two similar arms 22 and 24 which are joined at the fulcrum end 25. The gate area for mold filling is centrally located and is indicated by reference numeral 26. The grasping end of arm 22 is indicated by reference numeral 21 and the grasping end of arm 24 is indicated by reference numeral 23. The grasping ends 21 and 23 are mutually-opposed and in the as-molded condition are spaced-apart as shown in FIGS. 2A and 2B. Grasping ends 21 and 23 are adapted to be closed relative to each other for grasping food items by a user single-handedly. In addition, a cross-member or bridge 27 is provided between the arms 22 and 24 proximate to the fulcrum end 25. The opening or space created between the fulcrum end 25 and bridge 27 is denoted by reference numeral 28. One of the features of bridge 27 is that it serves to reduce the stresses encountered in the gate region when the tong arms are compressed together during normal use for grasping. However, this design (design “B”) also suffers from an inherent disadvantage in that the connecting bridge creates an area of stress concentration and tends to display breakage or failure at the mid-point of the bridge during normal use. The stress concentration is caused by a weld-line that is created during injection-molding of the part when two melt-flow fronts traveling alongside the two opposing arms meet at or about the center of the bridge. The presence of a weld-line (or fault-line) renders the tongs susceptible to breakage in that area.
FIGS. 2C and 2D show tongs 20 in one of the failure modes wherein like parts bear like reference markings. Specifically, FIGS. 2C and 2D show a failed bridge 27 due to stress concentration at the center of the bridge when the tong arms 22 and 24 are brought closer relative to one another. The failure results in the formation of a crack or split on the back edge of the bridge, typically at the weld-line, shown by reference numeral 29. The crack or split is the result of tension on the back edge of the bridge created during compression of arms 22 and 24 for closing respective grasping ends 21 and 23 when in use.
Generally speaking, the failures in tongs depend on a variety of factors including the physical design or construction; the material of construction; the type of food being handled; the weight of the food item to be grasped and lifted; the location where a user squeezes the arms of the tongs while grasping food items; repetitive cycles of compression and release of tong arms; and, the speed with which the two arms are closed together while grasping.
In order to improve the resistance to breakage of the tongs constructed according to the designs discussed above the tongs have been sometimes molded from a resin blend containing general purpose polystyrene (GPPS) and high-impact polystyrene (HIPS). It will be realized by those skilled in the art that a certain combination of flexibility and resilience is required to obtain a functional tongs article; however, it is also the experience of the inventors that incorporating large amounts of HIPS renders the tongs too flexible for use.
Thus, there is a need for improving the strength and breakage-resistance of prior art tongs. There is also a need for improving the failure rate in tongs without utilizing expensive resin blends or materials or resorting to an increase in the weight of tongs by using additional plastic resin. These and other needs as shall hereinafter appear are met by the tongs of the present invention.